Iptables is a firewall that allows or blocks traffic based on certain conditions. It is a command-line tool used to configure the Linux kernel's built-in firewall. Iptables uses a set of rules to decide whether to allow or block traffic. These rules can be based on criteria such as the source and destination of the traffic, the ports used, and the type of traffic. Iptables can be used to implement security policies, such as allowing only certain types of traffic or blocking traffic from certain locations.
What is iptables command?
The iptables command is used to configure the Linux kernel's built-in firewall. Iptables uses a set of tables which define the firewall rules. Each table contains a set of built-in chains and each chain is used to define a set of rules.
Iptables has six built-in tables:
• filter: This is the default table and it is used to filter network traffic.
• nat: This table is used for Network Address Translation (NAT).
• mangle: This table is used for specialized packet alteration.
• raw: This table is used for configuring exemptions from connection tracking.
• security: This table is used for Mandatory Access Control (MAC) security rules.
• user: This table is used for user-defined chains.
Each table contains a set of built-in chains. The filter table contains the following built-in chains:
• INPUT: This chain is used to filter incoming traffic.
• FORWARD: This chain is used to filter forward traffic.
• OUTPUT: This chain is used to filter outgoing traffic.
The nat table contains the following built-in chains:
• PREROUTING: This chain is used to filter incoming traffic before routing.
• OUTPUT: This chain is used to filter outgoing traffic before routing.
• POSTROUTING: This chain is used to
Why iptables are used in Linux?
Iptables is a user-space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores.
Iptables uses a set of tables which have chains that contain set of built-in or user-defined rules. When a packet arrives, the iptables firewall determines which table to use based on the packet's protocol (IPv4 or IPv6). Once the table is selected, the packet is compared against each chain in that table until it finds a match. If the packet doesn't match any rule in any of the chains, the packet is then compared against the policy for that table. The policy for a table can be set to ACCEPT, DROP or RETURN. If the policy is set to ACCEPT, the packet is allowed through the firewall. If the policy is set to DROP, the packet is dropped and no further processing is done. If the policy is set to RETURN, the packet is allowed through the firewall and any further processing for that table is stopped.
Iptables provides a wide range of options for the administrator including packet filtering, NAT, and packet mangling.
Packet filtering is a technique used to control network traffic by filtering out unwanted packets based on certain criteria. Packets that don't meet the criteria are dropped while packets that do meet the criteria are allowed through.
What type of firewall is iptables?
Iptables is a free and open source firewall that can be used to manage incoming and outgoing traffic on a Linux server. Iptables uses a set of rules to determine what type of traffic to allow or block. Iptables can be used to filter traffic based on a variety of criteria, such as source and destination IP address, port number, or protocol.
What are the 3 types of firewalls?
There are three primary types of firewalls:
1. Packet-filtering firewalls
2. Stateful inspection firewalls
3. Application-level gateways
Packet-filtering firewalls are the most basic type of firewall. They simply examine each incoming packet and compare it against a set of rules. If the packet matches a rule, it is allowed through; if not, it is blocked.
Stateful inspection firewalls keep track of the "state" of each connection passing through them. This allows them to more effectively block malicious traffic, as they can tell, for example, whether a given packet is part of a legitimate connection or not.
Application-level gateways act as proxies for specific applications. They inspect all traffic going to and from the application and can block traffic that is deemed to be malicious.